This invention relates generally to the ignition of a gas generant such as used for the inflation of inflatable devices such as airbag cushions used in inflatable restraint systems for vehicle occupants. In particular, the invention relates to such an ignition material which, upon combustion, produces a relatively small amount of particulate as compared to igniter compositions such as typically used in association with vehicle occupant restraint airbag cushions.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an "airbag cushion," that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in the event of a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Such systems typically also include one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden decelerations of the vehicle and to electronically trigger activation of the system. Upon actuation of the system, the cushion begins to be inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as an "inflator."
Many types of inflator devices have been disclosed in the art for the inflating of one or more inflatable restraint system airbag cushions. Inflator devices which form or produce inflation gas via the combustion of a gas generating material are well known. It is also known that certain of such inflator devices may use such generated gas to supplement stored and pressurized gas by the addition of high temperature combustion products, including additional gas products, produced by the burning of the gas generating material to a supply of the stored, pressurized gas. In some cases, the combustion products produced by the burning of a gas generating material may be the sole or substantially the sole source for the inflation gas issuing forth from a particular inflator device.
It is common that inflator devices include an initiator, such as a squib, and an igniter. In practice, upon receipt of an appropriate triggering signal from a crash or other selected deceleration sensor, the initiator activates causing the rapid combustion of the igniter material, which, in turn, ignites the gas generant.
The reduction in either or both the amount and concentration of particulate material that may issue forth from an inflator device upon the actuation thereof has been one focus of continuing improvement efforts. While such efforts have largely focused on gas generant composition formulations, igniter compositions may also significantly contribute to the particulate output of at least certain inflator devices.
A common or standard igniter formulation used for airbag inflators is composed of about 15 to about 30 weight percent (typically about 25 weight percent) boron and about 70 to about 85 weight percent (typically about 75 weight percent) potassium nitrate. In the art, this standard igniter formulation is commonly referred to as "BKNO.sub.3." While such an igniter composition has generally been useful and effective in such inflatable restraint system applications, the resulting combustion products typically include a significant portion which, though gaseous at the combustion temperatures and pressures typically occurring within the inflator device, condense and solidify into particulate at exhaust conditions, such as upon being exhausted into an associated airbag cushion.
As will be appreciated, the presence or occurrence of significant amounts of such condensible gaseous materials in inflatable restraint system airbag cushion inflation gases can be undesirable for various and numerous reasons. For example, such condensible gases are normally not easily removable or separable from the inflation gases via the application of simple filtration means. As will be appreciated, the presence of solid particulate material within inflatable restraint system airbag cushion and such as may subsequently be vented or passed to within the occupant compartment of the associated vehicle is generally undesired. For example, though such particulate material is normally variously sized, such particulate material typically includes a large amount of particulate within the respirable range for humans. Thus, the passage of such gas-borne particulate material into the passenger compartment of the corresponding vehicle, such as via conventional airbag venting, can result in undesired respiration of such particulate material by the driver and/or other vehicle passengers which in turn can cause consequent respiratory problems. Also, such particulate can easily become dispersed and airborne so as to appear to be smoke and such as may create a false impression that there is a fire in or about the vehicle.
There is a continuing need and demand for improved igniter materials for inflator device gas generating materials. In particular, there is a need and a demand for such an igniter material which may desirably be improved in one or more aspects such as safety, simplicity, effectiveness, economy and reliability. Further, in view of the above, there is a need and a demand for an igniter formulation such as may further reduce either or both the amount or concentration of particulate material that may issue forth from associated inflator devices upon the actuation thereof. Also, boron can be a relatively expensive component of common igniter formulations such as described above. As a result, there is a need and a demand for igniter formulations which reduce, minimize or possibly avoid the need for such relatively costly igniter composition components.
In addition, previous efforts at water processing of compositions containing magnesium or alloy combinations thereof have typically run into difficulties such as associated with the reaction of such materials with water. While solvent processing techniques are available, such processing typically requires or necessitates various additional costly processing steps in association with the environmentally desirable recovery or recycle of such solvent materials. Thus, there has been a need and demand for an improved method for water processing an igniter composition for a gas generant material, and which composition contains magnesium or an alloy combination thereof.